Population Genetics and Genetic Drift

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Questions and Answers

What is the result of a 32-base pair deletion in the Gene CCR5?

A nonfunctional protein due to a frameshift and premature termination (correct)

A mutation that causes AIDS

An increased expression of the receptor on cell surfaces

A functional protein that aids in HIV infection

What is the frequency of the AA genotype in a population, according to the Hardy-Weinberg Law?

p2 (correct)

2pq

What is the main factor that determines the unique response of an individual to environmental and pharmacological influences?

Genetic makeup (correct)

Dietary influences

Environmental factors

Pharmacological influences

What is the term for the collection of all alleles at a particular locus for the entire population?

Hypothetical gene pool Signup and view all the answers

Who are the two scientists credited with developing the Hardy-Weinberg Law?

Geoffrey Hardy and Wilhelm Weinberg Signup and view all the answers

What is the consequence of the loss of function of CCR5?

A benign trait Signup and view all the answers

What is the term for the study of genetic factors and their influence on the frequency and distribution of alleles and genotypes in populations?

Population genetics Signup and view all the answers

What is the main reason for the high frequency of a deleterious disease allele in a small population?

Random effects of environment or other chance occurrences Signup and view all the answers

What is the term for the phenomenon where a small subpopulation breaks off from a larger population, resulting in different gene frequencies?

Founder effect Signup and view all the answers

What is the name of the autosomal recessive condition that causes hepatic failure and renal tubular dysfunction due to a deficiency of fumarylacetoacetase?

Hereditary type I tyrosinemia Signup and view all the answers

What is the term for the variation in the frequency of genetic diseases among different ethnic groups?

Ethnic differences in genetic diseases Signup and view all the answers

What is the importance of ABO and Rh blood groups in medical applications?

Determining compatibility for blood transfusions Signup and view all the answers

What is the term for the unique variant protein products of polymorphic alleles that can affect how an individual interacts with the environment?

Chemical individuality Signup and view all the answers

What plays an important role in transplantation medicine?

The major histocompatibility complex (MHC) Signup and view all the answers

What is fitness (f) a measure of in terms of alleles?

The number of offspring of affected persons who survive to reproductive age Signup and view all the answers

What is the coefficient of selection (s)?

A measure of the loss of fitness Signup and view all the answers

What is a genetic lethal?

A genetic disorder that limits reproduction so severely that the fitness is zero Signup and view all the answers

What is heterozygote advantage?

Heterozygotes for some diseases have increased fitness over homozygotes for the normal allele Signup and view all the answers

What is gene flow?

The slow diffusion of genes across a barrier Signup and view all the answers

What is the term used to describe the process of crossing a reproductive barrier?

Migrant Signup and view all the answers

What are two factors that contribute to the development of differences in alleles and allele frequencies among ethnic groups?

Genetic drift, including nonrandom distribution of alleles among the individuals who founded particular subpopulations, and heterozygote advantage under environmental conditions that favor the reproductive fitness of carriers of deleterious mutations Signup and view all the answers

What is the situation described as when selective forces operate to both maintain a deleterious allele and remove it from the gene pool?

Balanced polymorphism Signup and view all the answers

What is the outcome of the joint effects of survival and fertility?

Fitness (f) Signup and view all the answers

What is the approximate percentage of alleles determining structurally different polypeptides in any one individual?

20% Signup and view all the answers

What is the primary focus of population genetics?

The study of the distribution of genetic variation in populations Signup and view all the answers

What is the result of being heterozygous for alleles determining structurally different polypeptides?

Co-expression of different polypeptides Signup and view all the answers

What is the significance of genetic variation in populations?

It affects the distribution of genetic variation within populations Signup and view all the answers

What is the main focus of the Hardy-Weinberg Law?

The maintenance of genetic equilibrium in populations Signup and view all the answers

What is the result of factors that disturb Hardy-Weinberg equilibrium?

A shift in the distribution of genetic variation within populations Signup and view all the answers

What is the significance of ethnic differences in the frequency of various genetic diseases?

It has implications for medical applications Signup and view all the answers

Study Notes

Genetic Variation in Individuals and Populations

Population genetics is the quantitative study of the distribution of genetic variation in populations and of how the frequencies of genes and genotypes are maintained or change over time.
Any individual is likely to be heterozygous for alleles determining structurally different polypeptides at approximately 20% of all genes.

Genetic Drift

Genetic drift explains a high frequency of a deleterious disease allele in a population.
Random effects of environment or other chance occurrences that are independent of the genotype and operating in a small population can produce significant changes in the frequency of the disease allele.
These changes are likely to smooth out as the population increases in size.

Founder Effect

When a small subpopulation breaks off from a larger population, the gene frequencies in the small population may be different from those of the population from which it originated.
The founder effect can lead to a high frequency of a deleterious disease allele in a population.

Ethnic Differences in the Frequency of Various Genetic Diseases

Ethnic differences in the frequency of various genetic diseases exist due to differences in gene frequencies between populations.
The human species of more than 8 billion members are separated into many subpopulations, or ethnic groups, distinguishable by appearance, geographical origin, and history.
Ancestry informative markers (AIMs) can be used to distinguish between ethnic groups.

Chemical Individuality

British physician Archibald Garrod discovered the importance of chemical individuality in determining compatibility for blood transfusions.
The ABO and Rh blood groups are important in determining compatibility for blood transfusions.
The major histocompatibility complex (MHC) plays an important role in transplantation medicine.

Biochemical Individuality

A striking degree of biochemical individuality exists within the human species in its makeup of enzymes and other gene products.
Each individual has a unique, genetically determined chemical makeup and responds in a unique manner to environmental, dietary, and pharmacological influences.

Genotypes and Phenotypes in Populations

Population genetics is concerned with both genetic and environmental factors that determine the frequency and distribution of alleles and genotypes in families and communities.
Genetic factors, such as mutation and reproduction, and environmental and societal factors, such as selection and migration, together determine the frequency and distribution of alleles and genotypes in populations.

Genetic Factors in Human Immunodeficiency Virus Resistance

The gene CCR5, which encodes a cell surface cytokine receptor, serves as an entry point for certain strains of the human immunodeficiency virus (HIV) that causes the acquired immunodeficiency syndrome (AIDS).
A 32-base pair deletion in this gene results in an allele (DCCR5) that encodes a nonfunctional protein.
Individuals homozygous for the DCCR5 allele do not express the receptor on their cell surface and are resistant to HIV infection.

The Hardy-Weinberg Law

The Hardy-Weinberg law is used to calculate genotype frequencies from allele frequencies.
The law rests on the assumptions that the population is large and matings are random with respect to the locus in question, allele frequencies remain constant over time, and there is no appreciable rate of mutation.
The law is described by the equation: p2 (chance of AA genotype), q2 (chance of aa genotype), and 2pq (chance of Aa genotype).

Factors That Disturb Hardy-Weinberg Equilibrium

Selection can disturb Hardy-Weinberg equilibrium by favoring certain genotypes over others.
The coefficient of selection (s) is a measure of the loss of fitness and is defined as 1 − f, where f is the fitness of the genotype.
Positive selection for heterozygotes can lead to a balanced polymorphism, where selective forces operate both to maintain a deleterious allele and to remove it from the gene pool.

Migration and Gene Flow

Migration can change allele frequency by the process of gene flow, defined as the slow diffusion of genes across a barrier.
Gene flow can lead to a change in allele frequency over time.
Factors that allow differences in alleles and allele frequencies among ethnic groups to develop include genetic drift, including nonrandom distribution of alleles among the individuals who founded particular subpopulations (founder effect), and heterozygote advantage under environmental conditions that favor the reproductive fitness of carriers of deleterious mutations.

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Description

This quiz covers the concepts of genetic variation in individuals and populations, including the quantitative study of genetic variation and genetic drift, which affects the frequency of genes and genotypes in a population.